Method for adjusting the overall luminosity of a bistable matrix screen displaying half-tones

Abstract

In a method for adjusting the overall luminosity of at least a part of a matrix screen, each row of the part is processed several times non-periodically to display half-tones. Each processing consists of a semi-selective operation followed by a selective operation. A delay is planned between the selective operation and the semi-selective operation, this delay being proportional to a weighting factor that is adjustable as a function of the desired overall luminosity and proportional to the time interval between the beginning of the treatment in progress and the beginning of the next treatment.

What is claimed is:  
     
       1. A method for adjusting an overall luminosity of at least a part of a screen comprising cells arranged in rows and columns and configured to display half tones, comprising the steps of: 
       applying to a first row a semi-selective operation followed by a selective operation, said selective operation being delayed from said semi-selective operation by a weighted delay time having a duration equal to a time interval between said application of said semi-selective operation and a next subsequent semi-selective operation multiplied by a factor k, said factor being chosen between 0 and 1 and being adjustable to the desired luminosity, and  
       repeating said applying step non-periodically to said first row, in order to display an image with half tones, the duration of a first weighted delay time between a first selective operation and a first semi-selective operation being different from the duration of a second weighted delay time between a second selective operation and a second semi-selective operation for a same value of said factor.  
     
     
       2. The method of claim  1 , further comprising the step of: 
       interleaving said applying step and said repeating step for said first row with corresponding applying steps and repeating steps for at least a second row of said rows.  
     
     
       3. The method of claim  2 , wherein said applying step comprises: 
       applying said semi-selective operation which is from a first group of sub-scans; and  
       applying said selective operation which is from a second group of sub-scans, wherein said first group of sub-scans and said second group of sub-scans are applied to all of said rows of said at least part of a screen in an ordered way.  
     
     
       4. The method of claim  3 , wherein said interleaving step comprises: 
       applying to a n order row a first sub-scan taken from the first group,  
       applying to a m order row a second sub-scan taken from the second group, where m is different than n,  
       applying to a p order row a third sub-scan taken from the first group, where p is different than n;  
       applying to a q order row a fourth sub-scan taken from the second group, where q is different than m;  
       applying to additional rows in a similar pattern each of the other remaining sub-scans from the first group and the second group until all of the sub-scans have been taken; and  
       repeating said steps of applying to a n, m, p, q, and additional order rows for corresponding n+1, m+1, p+1, q+1 and further additional rows in a similar manner until each of the sub-scans has been applied to corresponding rows of said part of the screen at least once.  
     
     
       5. The method of claim  1 , wherein said applying step comprises: 
       applying said selective operation to record a bit value on one of the cells; and  
       applying said semi-selective operation to erase one of the cells.  
     
     
       6. The method of claim  1 , wherein said applying step comprises: 
       applying said semi-selective operation to record a bit value on one of the cells; and  
       applying said selective operation to erase one of the cells.  
     
     
       7. The method of claim  1 , wherein said applying step comprises applying said semi-selective operation and said selective operation to a first row of a plasma panel. 
     
     
       8. The method of claim  1 , wherein said applying step comprises applying the semi-selective operation and the selective operation to a first row of a liquid crystal display. 
     
     
       9. An adjustable half-tone display system comprising: 
       a bistable matrix screen having rows and columns;  
       a first addressing device connected to said rows;  
       a second addressing device connected to said columns;  
       a control and synchronization device connected between the first addressing device and the second addressing device;  
       a first generator which sequentially generates a selective operation; and  
       a second generator which sequentially generates a semi-selective operation and a next subsequent semi-selective operation, wherein said first and second addressing devices, said control and synchronization device, and said first and second generators are configured to apply to a first row of said matrix screen the semi-selective operation followed by said selective operation, delayed the operation by a weighted delay time having a duration equal to the time interval between application of the semi-selective operation and the next subsequent semi-selective operation, multiplied by a factor k, chosen between 0 and 1 and adjustable to a desired luminosity,  
       and configured to repeatedly apply other semi-selective operations and selective operations non-periodically to said row in order to display an image with half-tones, wherein the duration of a first weighted delay time between a first selective operation and a first semi-selective operation being different from the duration of a second weighted delay time between a second selective operation and a second semi-selective operation for a same value of said factor.  
     
     
       10. The adjustable half-tone display system of claim  9  wherein: 
       said first generator comprises a read-only memory; and  
       said second generator comprises a read-only memory.  
     
     
       11. The adjustable half-tone display system of claim  9  wherein: 
       said first generator comprises a memory element which stores a first sequence; and  
       said second generator comprises a memory element which stores a second sequence.  
     
     
       12. The adjustable half-tone display system of claim  9  further comprising: 
       an overall user-actuated luminosity control device connected to at least one of said first generator and said second generator.  
     
     
       13. The adjustable half-tone display system of claim  12 , wherein said overall luminosity control device comprises a selector switch.